Synthesis, molecular structure and DFT studies of two heteroleptic nickel(II) s-triazine pincer type complexes

Abstract

Two new heteroleptic Ni(II) pincer complexes of s-triazine core ligand (L) were synthesized and characterized. The two complexes [NiL(H2O)2Cl]Cl; (1) and [NiL(H2O)3](ClO4)2.H2O; (2) showed a slightly distorted octahedral configuration around Ni(II), and L acts as a tridentate N-chelate with NiN bonds are generally shorter in 2 than 1. Using atoms in molecules (AIM) theory, the net interaction energies between Ni(II) and L are higher in 2 (96.75 kcal/mol) than in 1 (90.32 kcal/mol). The packing is dominated by O⋯H (45.0%) and Cl⋯H (16.0%) hydrogen bonds, respectively. Both complexes showed different extents of CH⋯O and anion-π stacking interactions. The MPW1PW91/TZVP method was used to predict the electronic properties of complexes 1 and 2. As a result of the interactions between the Ni(II) ion and ligand groups, the charge densities of nickel ion are reduced to 0.76–0.86 e in 1 and 0.87–0.98 e in 2. Also, its spin density is reduced to ∼1.73 e instead of 2.00 e in both complexes. Thermogravimetric analysis showed that 2 exploded at 281 °C in a fashion like the popcorn.